The invention relates generally to welding systems and, more particularly, to controlling parameters of an arc welding process.
A wide range of welding systems and welding control regimes have been implemented for various purposes. In continuous welding operations, gas metal arc welding (GMAW) techniques allow for formation of a continuous weld bead by feeding filler material shielded by inert or active gas from a welding torch. Electrical power is applied to the welding wire and a circuit is completed through the workpiece to sustain an arc that melts the wire and the workpiece to form the desired weld. Certain related processes do not use shielding gas, and may rely upon constituents in the welding wire for forming and protecting the progressing weld.
In its various forms, GMAW welding involves application of controlled voltages and currents to a welding wire that forms an electrode and is advanced towards a workpiece to create an arc between the electrode and the workpiece. The wire electrode is typically fed by a wire feeder coupled to a welding power supply, although in some systems, the wire feeder may be integrated into the power supply, or wire may be fed by a welding torch (e.g., “spoolgun”). In general, the welding torch may be held and controlled by a human operator, or may be part of an automated system, typically manipulated by a robotic device. Welding parameters may be set for all of these processes, including current and voltage levels, wire feed speeds, and so forth. For manual applications, travel speed (the rate of advancement of the torch to create the weld) is regulated by the operator, while in automated applications, this may be set in advance for particular welds and workpieces.
In GMAW and related welding processes, various welding parameters are controlled to maintain a desired arc length of the welding arc between the electrode and the workpiece. A constant arc length can provide a relatively consistent weld bead profile and weld penetration depth, which may enhance certain structural and aesthetic qualities of the weld. GMAW welding systems generally utilize voltage feedback to maintain a uniform voltage drop across the welding arc, which roughly corresponds with a uniform arc length. Unfortunately, it is difficult to accurately determine the voltage drop across the welding arc due to changes in the extension of the electrode as it is advanced toward the workpiece, as well as other voltage drops that are difficult to account for.